hikey: Drop support for 3.18 kernel

There are no more kernel binaries for this kernel so it does not make
sense to handle TARGET_KERNEL_USE=3.18. Remove the code, and custom
fstab.

Change-Id: I15dd43d4e5fb4acfcc15a256d1a5555f57cbc1f6
Signed-off-by: Alistair Strachan <astrachan@google.com>
diff --git a/hikey/BoardConfig.mk b/hikey/BoardConfig.mk
index 90bbc6c..13eed48 100644
--- a/hikey/BoardConfig.mk
+++ b/hikey/BoardConfig.mk
@@ -6,16 +6,12 @@
 TARGET_CPU_VARIANT := cortex-a53
 TARGET_2ND_CPU_VARIANT := cortex-a53
 
-ifeq ($(TARGET_KERNEL_USE), 3.18)
-BOARD_KERNEL_CMDLINE := console=ttyAMA3,115200 androidboot.console=ttyAMA3 androidboot.hardware=hikey firmware_class.path=/vendor/firmware efi=noruntime
-else
 ifeq ($(TARGET_KERNEL_USE), 4.19)
 BOARD_KERNEL_CMDLINE := console=ttyAMA3,115200 androidboot.console=ttyAMA3 androidboot.hardware=hikey firmware_class.path=/vendor/firmware efi=noruntime
 else
 # FIQ debugger is deprecated and we'll remoeve this once kernel support in prebuilts are yanked
 BOARD_KERNEL_CMDLINE := console=ttyFIQ0 androidboot.console=ttyFIQ0 androidboot.hardware=hikey firmware_class.path=/vendor/firmware efi=noruntime
 endif
-endif
 
 ifneq ($(TARGET_ANDROID_VERITY),)
 # Enable dtb fstab for treble, with verity and system-as-root
@@ -34,7 +30,7 @@
 endif
 
 ## printk.devkmsg only has meaning for kernel 4.9 and later
-## it would be ignored by kernel 3.18 and kernel 4.4
+## it would be ignored by kernel 4.4
 BOARD_KERNEL_CMDLINE += printk.devkmsg=on
 
 TARGET_NO_DTIMAGE := true